BuddhaMaster said:All the horned devils wear arm-attached guns on the original cover.

I never really noticed it, but I saw it now and it seems that only a few of them wear some kind of weapon on their left arm (like the Cyberdemon) while others have two normal arms.

I always considered those "generic devils" to be loosely based on Barons, although the ones with the "arm rifles" may be loosely inspired by the Cyberdemon (they don't seem to be any bigger, though).

In any case, cover art often sucks and takes too many liberties, like e.g. the snout of the "horned devil" in the foreground that looks more like a hyena or a babboon than demonic or goat-like. It's almost like the artist was told "just draw some nasty looking devils that want to tear the Doom Marine a new one", threw in some vague elements of the game and hey presto, the cover was ready.